Rotary reciprocating drive actuator having magnets and coils, capable of attaching a movable object

ABSTRACT

A movable magnet is configured by alternately magnetizing an even number of magnetic poles forming an South pole and an North pole; a number of magnetic poles of a core body is equal to a number of magnetic poles of the movable magnet; an even number of magnetic poles of the core body is respectively arranged to face the movable magnet with an air gap therebetween on the outer peripheral side of a shaft portion; and a drive unit is provided with a magnet position holding portion to face the movable magnet and magnetically attracts the movable magnet to a reference position. A drive unit is attached to one wall portion of the pair of wall portions of a base portion, and an angle sensor portion for detecting a rotation angle of the shaft portion is attached to the other wall portion of the pair of wall portions.

RELATED APPLICATION

This application claims the benefit of priority of Japanese PatentApplication No. 2019-225570 filed on Dec. 13, 2019, the contents ofwhich are all incorporated by reference as if fully set forth herein intheir entirety.

TECHNICAL FIELD

The present invention relates to a rotary reciprocating drive actuator.

BACKGROUND ART

For example, a rotation drive actuator is used in a scanner in amultifunction peripheral, a laser beam printer and other apparatuses.Specifically, a rotary reciprocating drive actuator changes a reflectionangle of a laser beam by rotating a mirror of the scanner in areciprocating manner to realize optical scanning with respect to anobject.

Conventionally, the scanner using a galvanometer motor as this type ofthe rotary reciprocating drive actuator is disclosed in such as PTL 1and PTL 2. Various types of the galvanometer motor, such as a coilmovable type in which a coil is attached to the mirror and a structuredisclosed in PTL 1, are known.

Incidentally, PTL 1 discloses a beam scanner in which four permanentmagnets are provided on a rotating shaft to which the mirror is attachedso as to be magnetized in the radial direction of the rotating shaft,and a core having magnetic poles around which the coil is wound isdisposed so as to sandwich the rotating shaft.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Application Laid-Open No. 2007-333873

PTL 2: Japanese Patent Application Laid-Open No. 2014-182167

SUMMARY OF INVENTION Technical Problem

By the way, in the rotary reciprocating drive actuator of the coilmovable type, heat generated by the coil during driving may adverselyaffect such as a surface state of the mirror, a bonding state of themirror to the rotating shaft and a shape of the mirror including a warp.Further, in the rotary reciprocating drive actuator of the coil movabletype, considering a heat generation of the coil at the time ofenergization, there are problems that an input current to the coil isdifficult to increase and a size and an amplitude of the mirror to be amovable body are difficult to increase. Further, there is a problem thatan assemblability is poor, because it is necessary to pull out wiringsto the coil to a fixed body side with respect to the mirror to be themovable body.

In PTL 1, since the magnets are disposed on the movable body side, theabove problem of the coil movable type can be solved. In PTL 1, however,two magnets per one core pole and a total of four magnets are requiredin order to make the magnet stationary at the neutral position withrespect to the core, that is, in order to position a switching portionof the magnetic pole of the magnet at the center of the core.

Thereby, there is a problem that the amplitude of the movable body isreduced, that is, a swing range is reduced, as compared with the casewhere an equivalent rotary reciprocating drive actuator is configured byusing two poles magnet, for example. Further, since at least fourmagnets are used, a number of parts is large, the structure iscomplicated and the assembly is difficult.

Further, in recent years, as a rotary reciprocating drive actuator usedin a scanner, a rotary reciprocating drive actuator that has rigidity,impact resistance and vibration resistance, improves assemblability andcan achieve high amplitude is desired on the assumption that the mirrorto be the movable body is enlarged and the like.

Further, as also described in PTL 1, the rotary reciprocating driveactuator is provided with an angle sensor for detecting a rotation angleof the rotation shaft connected to the mirror. A scanning accuracy as ascanner greatly depends on a detection accuracy of the angle sensor. Inorder to improve the detection accuracy of the angle sensor, it isnecessary to adjust a mounting position of the angle sensor with highaccuracy so that the relative relationship between the angle sensor andthe other components of the rotary reciprocating drive actuator such asthe mirror becomes a determined relationship. Such requirements make itdifficult to assemble the rotary reciprocating drive actuator.

The present invention has been made in consideration of the abovepoints, and provides a rotary reciprocating drive actuator which can beeasily assembled and can drive a movable object at a high amplitude.

Solution to Problem

According to one aspect of a rotary reciprocating drive actuator of thepresent invention, the rotary reciprocating drive actuator comprising:

-   -   a base portion;    -   a movable magnet fixed to a shaft portion to which a movable        object is connected; and    -   a drive unit having a core body and a coil body for generating a        magnetic flux in the core body when current is supplied, and        driving the movable magnet in a rotary reciprocating manner by        an electromagnetic interaction between the magnetic flux        generated from the core body and the movable magnet,    -   wherein the movable magnet is formed in a ring shape, and is        configured by alternately magnetizing an even number of magnetic        poles forming an S-pole and an N-pole at an outer periphery of        the shaft portion;    -   a number of magnetic poles of the core body and a number of        magnetic poles of the movable magnet are equal to each other;    -   an even number of magnetic poles of the core body is        respectively arranged to face the movable magnet with an air gap        therebetween on the outer peripheral side of the shaft portion;    -   the drive unit is provided with a magnet position holding        portion which is a magnetic material provided to face the        movable magnet and magnetically attracts the movable magnet to a        reference position;    -   a pair of wall portions is erected on the base portion to        rotatably support the shaft portion via a bearing, and the        movable object is disposed between the pair of wall portions;        and    -   the drive unit is attached to one wall portion of the pair of        wall portions, and an angle sensor portion for detecting the        rotation angle of the shaft portion is attached to the other        wall portion of the pair of wall portions.

Advantageous Effects of Invention

According to the present invention, since the magnet position holdingportion for magnetically attracting the movable magnet to the referenceposition is provided, even if the movable object is a large sizedmirror, it can be driven at a high amplitude. Further, since the anglesensor portion is attached to the other wall portion with respect to thewall portion to which the drive unit is attached in the pair of wallportions, it can be easily assembled.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an external perspective view of a rotary reciprocating driveactuator of an embodiment;

FIG. 2 is an exploded perspective view of the rotary reciprocating driveactuator;

FIG. 3 is a side view of the rotary reciprocating drive actuator of FIG.1 viewed from a drive unit side;

FIG. 4 is a view for explaining an operation of a magnetic circuit ofthe rotary reciprocating drive actuator;

FIG. 5 is a view for explaining the operation of the magnetic circuit ofthe rotary reciprocating drive actuator;

FIG. 6 is a block diagram showing a configuration of main parts of ascanner system using the rotary reciprocating drive actuator;

FIG. 7 is an external perspective view showing an exemplaryconfiguration of the scanner system;

FIG. 8 is an external perspective view showing another exemplaryconfiguration of the scanner system;

FIG. 9 is an external perspective view of the rotary reciprocating driveactuator of another embodiment; and

FIG. 10 is an exploded perspective view of the rotary reciprocatingdrive actuator of another embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

<1> Entire Configuration of a Rotary Reciprocating Drive Actuator

FIG. 1 is an external perspective view of rotary reciprocating driveactuator 100 of the embodiment. FIG. 2 is an exploded perspective viewof rotary reciprocating drive actuator 100.

Rotary reciprocating drive actuator 100 is used, for example, in a LIDAR(Laser Imaging Detection and Ranging) apparatus. Note that, rotaryreciprocating drive actuator 100 is also applicable to a scanner in amultifunction peripheral, a laser beam printer and other apparatuses.

Rotary reciprocating drive actuator 100 is roughly divided into baseportion 110; mirror portion 120 rotatably supported by base portion 110;drive unit 200 for driving mirror portion 120 in a rotary reciprocatingmanner; and angle sensor portion 130 for detecting a rotational angleposition of mirror portion 120.

As can be seen from FIG. 2 , mirror 121 is attached to one surface ofsubstrate 122 in mirror portion 120. Shaft portion 141 is inserted intoinsertion hole 122 a of substrate 122, and substrate 122 and shaftportion 141 are fastened.

Base portion 110 is a member having a substantially U-shaped crosssection and having a pair of wall portions 111 a and 111 b. Insertionhole 112 through which shaft portion 141 is inserted is formed in eachof the pair of wall portions 111 a and 111 b. Further, notched holes 113communicating insertion holes 112 and the outer edges of wall portions111 a and 111 b are formed in the pair of wall portions 111 a and 111 b,respectively.

Thus, shaft portion 141 can be disposed at positions of insertion holes112 through notched holes 113 in a state where mirror portion 120 isfastened to shaft portion 141. In the case where notched holes 113 arenot provided, a complicated assembly operation is required in whichshaft portion 141 is inserted into both insertion holes 112 of wallportions 111 a, 111 b and insertion hole 122 a of substrate 122 whilemirror portion 120 is disposed between the pair of wall portions 111 aand 111 b, and shaft portion 141 and substrate 122 are fastened. Incontrast, in the present embodiment, since notched holes 113 are formed,shaft portion 141 to which mirror portion 120 is fastened in advance canbe easily inserted into insertion holes 112.

Ball bearings 151 are attached to both ends of shaft portion 141. Ballbearings 151 are mounted to bearing mounting portions 114 formed at thepositions of insertion holes 112 of the pair of wall portions 111 a and111 b. Thus, shaft portion 141 is rotatably attached to base portion 110via ball bearings 151, and mirror portion 120 to be the movable objectis disposed between the pair of wall portions 111 a and 111 b.

Further, movable magnet 161 is fastened to one end of shaft portion 141.Movable magnet 161 is disposed inside of drive unit 200 and is driven ina rotary reciprocating manner by a magnetic flux generated by drive unit200.

As described above, in the present embodiment, shaft portion 141 towhich mirror portion 120 to be the movable object is attached ispivotally supported by the pair of wall portions 111 a and 111 b of baseportion 110 so as to support mirror portion 120 from both sides. Thus,mirror portion 120 is supported more firmly than the case where shaftportion 141 is pivotally supported in a cantilever manner, and a shockresistance and a vibration resistance are improved.

As can be seen from FIG. 2 , drive unit 200 has core body 210 and coilbody 220. A coil is provided with a winding inside of coil body 220.Core body 210 includes first core body 211 and second core body 212.Similarly, coil body 220 includes first coil body 221 and second coilbody 222. Coil body 220 is mounted so as to be inserted into a part ofcore body 210. Thus, when the coil of coil body 220 is energized, corebody 210 is excited.

Core body 210 and coil body 220 are fixed to fixing plate 250, andfixing plate 250 is fixed to wall portion 111 a of base portion 110 viafastening members 251.

Incidentally, in the present embodiment, drive unit 200 further includesbridging core 230 and magnet position holding portion 240. Bridging core230 has the same structure as core body 210. Magnet position holdingportion 240 is made of a magnet. A position of movable magnet 161 ismagnetically attracted to a movement reference position by a magneticforce of magnet position holding portion 240. This will be described indetail later.

In the example of the present embodiment, core body 210 and bridgingcore 230 are laminated cores, and are formed by laminating, for example,silicon steel plates.

Angle sensor portion 130 includes circuit board 131; optical sensor 132and connector 133 mounted on circuit board 131; encoder disk 134; andcase 135. Circuit board 131 is fixed to case 135 by fastening members136. Case 135 is fixed to wall portion 111 b by fastening members 137.

Encoder disk 134 is mounted by fastening to shaft portion 141 viamounting member 138, and rotates integrally with movable magnet 161 andmirror portion 120. That is, mounting member 138 has an insertion holethrough which shaft portion 141 is inserted and fastened, and a flangeportion to which encoder disk 134 is abutted and fastened, and mountingmember 138 is fixed to both shaft portion 141 and encoder disk 134. As aresult, a rotational position of encoder disk 134 is the same as arotational position of shaft portion 141. Optical sensor 132 emits lightto encoder disk 134 and detects the rotational position (angle) ofencoder disk 134 based on the reflected light. Thus, the rotationalpositions of movable magnet 161 and mirror portion 120 can be detectedby optical sensor 132.

In the rotary reciprocating drive actuator 100 of the presentembodiment, the movable body having movable magnet 161 and shaft portion141, and drive unit 200 having coil body 220, core body 210, and thelike are attached to an outer surface side of one wall portion 111 a ofthe pair of wall portions 111 a and 111 b of base portion 110. On theother hand, angle sensor portion 130 for detecting the rotation angle ofshaft portion 141 is attached to an outer surface side of the other wallportion 111 b of the pair of wall portions 111 a and 111 b of baseportion 110.

This makes it easy to remove angle sensor portion 130 and adjust anassembly position thereof. Since angle sensor portion 130 can be easilyremoved, angle sensor portion 130 can be easily replaced when a failureoccurs in angle sensor portion 130. Further, angle sensor portion 130can be assembled at the final stage of assembly. As a result, theexpensive angle sensor portion 130 can be assembled after it isconfirmed that the assembly of the other components is normal.Therefore, a risk of wasting the expensive angle sensor portion 130 dueto the assembly failure of the other components can be suppressed.

<2> Detailed Configuration and Operation of Rotary Reciprocating DriveActuator

Next, detailed configuration and operation of rotary reciprocating driveactuator 100 will be described with reference to FIGS. 3 to 5 .

FIG. 3 is a side view of rotary reciprocating drive actuator 100 of FIG.1 viewed from the left side of FIG. 1 . That is, drive unit 200 ismainly shown in FIG. 3 .

In rotary reciprocating drive actuator 100, the movable body includingmovable magnet 161, shaft portion 141 and other potions is rotatablyheld by the magnetic attraction force, that is, a magnetic spring,between magnet position holding portion 240 and movable magnet 161, sothat the movable body is positioned at the movement reference positionin the normal state. Here, the normal state is a state where coil body220 is not energized.

Positioning the movable body at the movement reference position meansthat movable magnet 161 is positioned at a neutral position with respectto magnetic poles 211 a and 212 a of core body 210 excited by coil body220 in the present embodiment, and it is a position capable of rotatingsimilarly in either one direction and the other direction around theshaft (normal rotation and reverse rotation viewed from shaft portion141 side). In other words, the movement reference position at whichmagnet position holding portion 240 magnetically attracts movable magnet161 is a rotational center position of the rotating reciprocation ofmovable magnet 161. When the movable body is positioned at the movementreference position, magnetic pole switching portions 161 c of movablemagnet 161 are positioned at positions facing the magnetic poles of coilbody 220 side.

By the cooperation of movable magnet 161 and coil body 220, shaftportion 141 of the movable body rotates in one direction and in theother direction around the shaft from the movement reference position ina reciprocating manner with respect to base portion 110.

Movable magnet 161 is formed in a ring shape, and has an even number ofmagnetic poles 161 a, 161 b in which an S-pole (a South pole) and anN-pole (a North pole) are alternately magnetized in a directionorthogonal to the rotational axis direction of shaft portion 141 at anouter periphery of shaft portion 141. Although movable magnet 161 ismagnetized to two poles in the present embodiment, it may be magnetizedto two or more poles depending on an amplitude at the time of movement.

The even number of magnetic poles 161 a and 161 b has magnetizationsurfaces of different polarities facing opposite direction to each otheracross shaft portion 141. In the present embodiment, magnetic poles 161a and 161 b have different polarities in which a plane along the axialdirection of shaft portion 141 is as a boundary thereof.

Further, the even number of magnetic poles 161 a and 161 b is configuredto magnetize at equal intervals at the outer periphery of shaft portion141.

As described above, in movable magnet 161, the even number of magneticpoles 161 a and 161 b forming the S-pole and the N-pole is alternatelyarranged at the outer periphery of shaft portion 141, and the magneticpoles 161 a and 161 b are arranged at equal intervals.

More specifically, in movable magnet 161, each of semicircular portionsconstitutes different magnetic poles 161 a and 161 b. Arc shaped curvedsurfaces of the semicircular portions are magnetization surfaces ofdifferent magnetic poles 161 a and 161 b, and the magnetization surfacesof different magnetic poles 161 a and 161 b are configured to extend ina circumferential direction around the shaft. In other words, themagnetization surfaces of magnetic poles 161 a and 161 b are arranged ina direction orthogonal to the axial direction of shaft portion 141, andare rotated to be able to face to magnetic pole 211 a of first core body211 and magnetic pole 212 a of second core body 212, respectively.

A number of magnetic poles of movable magnet 161 is equal to a number ofmagnetic poles of core body 210.

Magnetic pole switching portions 161 c of magnetic poles 161 a and 161 bof movable magnet 161 are located at positions facing center positionsin a width direction of magnetic pole 211 a of first core body 211 andmagnetic pole 212 a of second core body 212 when coil body 220 is notenergized.

First core body 211 and second core body 212 are parallel to each other,and have core portions 211 b and 212 b (see FIG. 4 ) which are formed soas to sandwich movable magnet 161. First coil body 221 and second coilbody 222 are respectively extrapolated to core portions 211 b and 212 b.Bridging core 230 is provided to be bridged between one end portions ofcore portions 211 b and 212 b, and magnetic poles 211 a and 212 a areformed continuously on the other end portions of core portions 211 b and212 b.

As described above, core body 210 has core portions 211 b and 212 b towhich first coil body 221 and second coil body 222 are extrapolated;magnetic poles 211 a and 212 a; and bridging core 230 provided to bebridged between the end portions opposite to magnetic poles 211 a and212 a. That is, core body 210 is configured from three split bodies.Among these split bodies, bridging core 230 is provided with magnetposition holding portion 240.

Two magnetic poles 211 a and 212 b are disposed to face each other so asto sandwich movable magnet 161 with air gap G between them and the outerperiphery of movable magnet 161.

Magnet position holding portion 240, which is disposed to face movablemagnet 161 with air gap G therebetween, is attached to bridging core 230so as to project convexly toward movable magnet 161 side.

Magnet position holding portion 240 is, for example, a magnet whoseopposing surface is magnetized to the N-pole (see FIG. 4 ). Magnetposition holding portion 240 may be formed integrally with bridging core230.

Magnet position holding portion 240 functions as a magnetic springtogether with movable magnet 161 by the magnetic attraction forcegenerated between it and movable magnet 161, and positions and holds theposition of rotating movable magnet 161 at the movement referenceposition.

Magnet position holding portion 240 is a magnet magnetized towardmovable magnet 161. Magnet position holding portion 240 positionsmagnetic pole switching portions 161 c of movable magnet 161 atpositions facing magnetic poles 211 a and 212 a when movable magnet 161is positioned at the movement reference position. As described above,magnet position holding portion 240 and movable magnet 161 are attractedto each other, and magnet position holding portion 240 can positionmovable magnet 161 at the movement reference position. Thus, magneticpole switching portions 161 c of movable magnet 161 face magnetic pole211 a of first core body 211 and magnetic pole 212 a of second core body212. At this position, drive unit 200 generates the maximum torque tostably drive the movable body.

Further, since movable magnet 161 is magnetized with two poles, themovable object can be easily driven at a high amplitude and vibrationperformance can be improved by cooperation with core body 210.

FIGS. 4 and 5 are views for explaining an operation of a magneticcircuit of rotary reciprocating drive actuator 100.

When coil body 220 (221, 222) is not energized, movable magnet 161 ispositioned at the movement reference position by the magnetic attractionforce between magnet position holding portion 240 and movable magnet161, that is, the magnetic spring.

In this movement reference position (hereinafter, the movement referenceposition may be referred to as a normal state), one of magnetic poles161 a and 161 b of movable magnet 161 is attracted to magnet positionholding portion 240, and magnetic pole switching portions 161 c arepositioned at positions facing the center positions of magnetic pole 211a of first core body 211 and magnetic pole 212 a of second core body212.

When coil body 220 is energized, coil body 220 (221, 222) excite firstcore body 211 and second core body 212.

When coil body 220 is energized in the direction shown in FIG. 4 ,magnetic pole 211 a is magnetized to the N-pole, and magnetic pole 212 ais magnetized to the S-pole.

As a result, in first core body 211, a magnetic flux is formed in whichthe magnetic flux is emitted from magnetic pole 211 a magnetized to theN-pole to movable magnet 161, flows through movable magnet 161, magnetposition holding portion 240, and bridging core 230 in this order, andenters into core portion 211 b.

In second core body 212, the magnetic flux is emitted from core portion212 b to bridging core 230 side, flows through bridging core 230, magnetposition holding portion 240, and movable magnet 161 in this order, andenters magnetic pole 212 a.

As a result, magnetic pole 211 a magnetized to the N-pole is attractedto the S-pole in movable magnet 161, magnetic pole 212 a magnetized tothe S-pole is attracted to N-pole in movable magnet 161, a torque in theF direction is generated around the axis of shaft portion 141 in movablemagnet 161, and movable magnet 161 rotates in the F direction.Accordingly, shaft portion 141 also rotates, and mirror portion 120fixed to shaft portion 141 also rotates.

Next, as shown in FIG. 5 , when the energization direction of coil body220 is switched to the opposite direction, magnetic pole 211 a ismagnetized to the S-pole, magnetic pole 212 a is magnetized to theN-pole, and the flow of the magnetic flux is also reversed.

As a result, magnetic pole 211 a magnetized to the S-pole is attractedto the N-pole in movable magnet 161, magnetic pole 212 a magnetized tothe N-pole is attracted to the S-pole in movable magnet 161, a torque inthe direction opposite to the F direction is generated around the axisof shaft portion 141 in movable magnet 161, and movable magnet 161rotates in the direction opposite to the F direction. Accordingly, shaftportion 141 also rotates in the opposite direction, and mirror portion120 fixed to shaft portion 141 also rotates in the opposite direction.By repeating these motions, rotary reciprocating drive actuator 100drives mirror portion 120 in a rotary reciprocating manner.

In practice, rotary reciprocating drive actuator 100 is driven by analternating current wave input from a power supply unit (for example,corresponding to drive signal supply unit 303 in FIG. 6 ) to coil body220. That is, the energization direction of coil body 220 isperiodically switched, and the torque in the F direction around the axisand the torque in the direction opposite to the F direction (−Fdirection) alternately act on the movable body. Thus, the movable bodyis driven in a rotary reciprocating manner.

Incidentally, at the time of switching the energization direction, themagnetic attraction force between magnet position holding portion 240and movable magnet 161 is generated, that is, magnetic spring torque FM(FIG. 4 ) or −FM (FIG. 5 ) is generated by the magnetic spring, andmovable magnet 161 is urged to the movement reference position.

The driving principle of rotary reciprocating drive actuator 100 will bebriefly described below. In rotary reciprocating drive actuator 100 ofthe present embodiment, when the moment of inertia of the movable bodyis J [kg·m²] and the spring constant in the torsional direction of themagnetic spring (magnetic poles 211 a and 212 a, magnet position holdingportion 240, and movable magnet 161) is K_(sp), the movable bodyvibrates (rotary reciprocates) with respect to base portion 110 at aresonance frequency F_(r) [Hz] calculated by the equation (1).

$\begin{matrix}{F_{r} = {\frac{1}{2\pi}\sqrt{\frac{K_{sp}}{J}}}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$F_(r): Resonance frequency [Hz]J: Moment of inertia [kg·m²]K_(sp): Spring constant [N·m/rad]

Since the movable body constitutes a mass portion in a vibration modelof a spring-mass system, when an alternating current wave having afrequency equal to the resonance frequency F_(r) of the movable body isinputted to coil body 220, the movable body enters a resonance state.That is, by inputting the alternating current wave having a frequencysubstantially equal to the resonance frequency F_(r) of the movable bodyto coil body 220 from the power supply unit, the movable body can beefficiently vibrated.

A motion equation and a circuit equation showing the driving principleof rotary reciprocating drive actuator 100 are shown below. Rotaryreciprocating drive actuator 100 is driven based on the motion equationexpressed by the equation (2) and the circuit equation expressed by theequation (3).

$\begin{matrix}{{J\frac{d^{2}{\theta(t)}}{{dt}^{2}}} = {{K_{t}{i(t)}} - {K_{sp}{\theta(t)}} - {D\frac{d{\theta(t)}}{dt}} - T_{Loss}}} & \left\lbrack {{Equation}2} \right\rbrack\end{matrix}$J: Moment of inertia [kg·m²]θ(t): Rotation angle [rad]K_(t): Torque constant [N·m/A]i(t): Current [A]K_(sp): Spring constant [N·m/rad]D: Damping coefficient [N·m/(rad/s)]T_(Loss): Load torque [N·m]

$\begin{matrix}{{e(t)} = {{{Ri}(t)} + {L\frac{{di}(t)}{dt}} + {K_{e}\frac{d{\theta(t)}}{dt}}}} & \left\lbrack {{Equation}3} \right\rbrack\end{matrix}$e(t): Voltage [V]R: Resistance [Ω]L: Inductance [H]K_(e): Counter electromotive force constant [V/(rad/s)]

That is, the moment of inertia J [kg·m²], the rotation angle θ(t) [rad],the torque constant K_(t) [N·m/A], the current i(t) [A], the springconstant K_(sp) [N·m/rad], the damping coefficient D [N·m/(rad/s)], theload torque T_(Loss) [N·m], and the like of the movable body in rotaryreciprocating drive actuator 100 can be appropriately changed within therange satisfying the equation (2). Further, the voltage e(t) [V], theresistance R [Ω], the inductance L [H], and the counter electromotiveforce constant K_(e) [V/(rad/s)] can be appropriately changed within therange satisfying the equation (3).

As described above, rotary reciprocating drive actuator 100 canefficiently obtain a large vibration output when the coil is energizedby the alternating current wave corresponding to the resonance frequencyF_(r) determined by the moment of inertia J of the movable body and thespring constant K_(sp) of the magnetic spring.

According to rotary reciprocating drive actuator 100 of the presentembodiment, since a torque generation efficiency is high, heat is hardto transfer to mirror 121 which is the movable object, and as a result,a flatness of a reflection surface of mirror 121 can be ensured withhigh accuracy. Further, a manufacturing efficiency is high, an assemblyaccuracy is good, and even if the movable object is a large sizedmirror, it can be driven at a high amplitude.

Note that, rotary reciprocating drive actuator 100 of the presentembodiment can be driven by resonance, but can also be driven bynon-resonance.

<3> Overview Configuration of Scanner System

Next, a configuration of a scanner system using rotary reciprocatingdrive actuator 100 will be briefly described.

FIG. 6 is a block diagram showing an essential configuration of scannersystem 300A using rotary reciprocating drive actuator 100.

Scanner system 300A includes laser emitting unit 301; laser control unit302; drive signal supply unit 303; and position control signalcalculation unit 304 in addition to rotary reciprocating drive actuator100.

Laser emitting unit 301 includes, for example, an LD (laser diode) to bea light source; a lens system for converging a laser beam output fromthe light source, and the like. Laser control unit 302 controls laseremitting unit 301. The laser beam obtained by laser emitting unit 301 isincident on mirror 121 of rotary reciprocating drive actuator 100.

Position control signal calculation unit 304 generates and outputs adrive signal for controlling shaft portion 141 (mirror 121) to be thetarget angular position with reference to the angular position of shaftportion 141 (mirror 121) acquired by angle sensor portion 130 and thetarget angular position. For example, position control signalcalculation unit 304 generates a position control signal on the basis ofthe obtained angular position of shaft portion 141 (mirror 121) and asignal indicating the target angular position converted using sawtoothwaveform data, and the like stored in a waveform memory which is notillustrated, and outputs the position control signal to drive signalsupply unit 303.

Based on the position control signal, drive signal supply unit 303supplies the drive signal to coil body 220 of rotary reciprocating driveactuator 100 such that the angular position of shaft portion 141 (mirror121) becomes a desired angular position. Thus, scanner system 300A canemit a scanning light from rotary reciprocating drive actuator 100 to apredetermined scanning area.

FIG. 7 is an external perspective view showing an example of theconfiguration of the scanner system, in which the same reference signsare assigned to the corresponding parts in FIG. 1 . In scanner system300C, laser unit 410 is provided on base portion 110. Laser unit 410includes laser emitting unit 411 and laser light receiving unit 412.Thus, a laser beam emitted from laser emitting unit 411 is reflected bymirror portion 120 of rotary reciprocating drive actuator 100 to be ascanning light, and irradiated to a scanning object. The scanning lightreflected by the scanning object is received by laser light receivingunit 412 through mirror portion 120. Note that, in rotary reciprocatingdrive actuator 100 of scanner system 300C, as compared with rotaryreciprocating drive actuator 100 of FIG. 1 , a bottom plate of baseportion 110 is extended in a depth direction in the drawing, and laserunit 410 is installed in this extended portion.

FIG. 8 is an external perspective view showing another configurationexample of the scanner system, in which the same reference signs areassigned to the corresponding parts in FIG. 7 . Scanner system 300D hasthe same configuration as scanner system 300C except that laser unit 410is disposed at a different position.

As shown in FIGS. 7 and 8 , since laser unit 410 is provided in baseportion 110 of rotary reciprocating drive actuator 100, laser unit 410can be easily and accurately attached to rotary reciprocating driveactuator 100.

Here, if a function as a scanner is to be realized, laser unit 410 maynot have laser light receiving unit 412 but may have only laser emittingunit 411. However, in the present embodiment, since laser unit 410 alsohas laser light receiving unit 412, and laser unit 410 is provided inbase portion 110 of rotary reciprocating drive actuator 100, as aresult, laser light receiving unit 412 as the light detecting unit is aconfiguration in which laser light receiving unit 412 is directlyattached to the scanner portion. Thus, the positioning accuracy of thelaser light receiving unit to the scanner portion can be easilyenhanced.

<4> Summary

As described above, rotary reciprocating drive actuator 100 of thepresent embodiment includes base portion 110; movable magnet 210 fixedto shaft portion 141 to which the movable object (mirror portion 120 inthe example of the embodiment) is connected; and drive unit 200 havingcore body 210 and coil body 220 for generating the magnetic flux in corebody 161 when the current is supplied, and driving movable magnet 161 ina rotary reciprocating manner by the electromagnetic interaction betweenthe magnetic flux generated from core body 210 and movable magnet 161.Further, in rotary reciprocating drive actuator 100, movable magnet 161is formed in the ring shape, and is configured by alternatelymagnetizing the even number of magnetic poles forming the S-pole and theN-pole at the outer periphery of shaft portion 141; the number ofmagnetic poles of core body 210 and the number of magnetic poles ofmovable magnet 161 are equal to each other; the even number of magneticpoles of core body 210 is respectively arranged to face movable magnet161 with the air gap therebetween on the outer peripheral side of shaftportion 141; and drive unit 200 is provided with magnet position holdingportion 240 which is a magnetic material provided to face movable magnet161 and magnetically attracts movable magnet 161 to a referenceposition.

Thus, since movable magnet 161 is magnetically attracted to the neutralposition (movement reference position) by magnet position holdingportion 240 every time the energization direction is switched, goodenergy efficiency, good responsiveness, and high amplitude rotaryreciprocating drive are realized. Further, compared with the rotaryreciprocating drive actuator of the coil movable type, the heatgenerated by coil body 220 is hard to transfer to the movable object,and when the movable object is a mirror, it is possible to preventadverse effects (bond deterioration, warpage, etc.) of the heat fromaffecting the mirror.

In addition, in rotary reciprocating drive actuator 100 of the presentembodiment, the pair of wall portions 111 a and 111 b for rotatablysupporting shaft portion 141 via bearings (ball bearings 151) areprovided in base portion 110, the movable object (mirror portion 120 inthe example of the embodiment) is disposed between the pair of wallportions 111 a and 111 b. Drive unit 200 is attached to the outersurface side of one wall portion 111 a of the pair of wall portions 111a and 111 b, and angle sensor portion 130 for detecting the rotationangle of shaft portion 141 is attached to the outer surface side of theother wall portion 111 b of the pair of wall portions 111 a and 111 b.

This makes it easy to remove angle sensor portion 130 and adjust theassembly position thereof. Since angle sensor portion 130 can be easilyremoved, angle sensor portion 130 can be easily replaced when thefailure occurs in angle sensor portion 130. Further, angle sensorportion 130 can be assembled at the final stage of assembly. As aresult, the expensive angle sensor portion 130 can be assembled after itis confirmed that the assembly of the other components is normal.Therefore, the risk of wasting the expensive angle sensor portion 130due to the assembly failure of the other components can be suppressed.

In one aspect of the present invention, the reference position at whichmagnet position holding portion 240 magnetically attracts movable magnet161 is the rotational center position of the rotating reciprocation ofmovable magnet 161.

In one aspect of the present invention, in movable magnet 161, the evennumber of magnetic poles is magnetized at equal intervals at the outerperiphery of shaft portion 141.

In one aspect of the present invention, magnet position holding portion240 is disposed at the position between the even number of magneticpoles of core body 210 and at the position facing movable magnet 161 inthe radial direction of movable magnet 161.

These configurations can maximize a driving torque and stabilize adirection of the driving torque.

The above embodiments are merely specific examples for carrying out thepresent invention, and the technical scope of the present inventionshould not be construed to be limited by them. That is, the presentinvention can be implemented in a variety of ways without departing fromthe spirit or essential features thereof.

In the above embodiment, the case where wall portion 111 b to attachangle sensor portion 130 is formed integrally with base portion 110 isdescribed. A wall portion to attach angle sensor portion 130, however,may not be formed integrally with base portion 110 but may be attachedto the base portion later.

Specifically, as shown in FIG. 9 in which the same reference signs areassigned to the corresponding portions in FIG. 1 and FIG. in which thesame reference signs are assigned to the corresponding portions in FIG.2 , rotary reciprocating drive actuator 100A has an L shaped baseportion 110′. In rotary reciprocating drive actuator 100A, wall portion111 c to which angle sensor portion 130 is attached to the inner surfaceis attached to base portion 110′. In this configuration, since wallportion 111 c can be removed from or relatively moved with respect tobase portion 110′, angle sensor portion 130 can also be easily removedand the assembling position can be easily adjusted. However, as in theabove embodiments, the configuration in which angle sensor portion 130is attached to the outer surface side of wall portion 111 b is easier toremove and adjust the assembling position of angle sensor portion 130.

In the above embodiments, the case where ball bearings 151 are used asbearings for rotatably attaching shaft portion 141 to base portion 110is described. The present invention, however, is not limited thereto,and an air bearing, an oil bearing and other bearings may be used asbearings.

In the above embodiments, the case where drive unit 200 is mounted onthe outer surface side of wall portion 111 a is described. The positionof drive unit 200, however, is not limited thereto. Dive unit 200 may bemounted, for example, on the inner surface side of wall portion 111 a.

In the above embodiments, the case where the movable object driven byrotary reciprocating drive actuator 100, that is, the movable objectattached to shaft portion 141 is mirror portion 120 is described. Themovable object, however, is not limited thereto. For example, a cameraor the like may be the movable object.

INDUSTRIAL APPLICABILITY

The present invention is suitable for a scanner, for example.

REFERENCE SIGNS LIST

-   100, 100A Rotary reciprocating drive actuator-   110, 110′ Base portion-   111 a, 111 b, 111 c Wall portion-   112 Insertion hole-   113 Notched hole-   114 Bearing mounting portion-   120 Mirror portion-   121 Mirror-   122 Substrate-   122 a Insertion hole-   130 Angle sensor portion-   131 Circuit board-   132 Optical sensor-   133 Connector-   134 Encoder disk-   135 Case-   136, 137, 251 Fastening member-   138 Mounting member-   141 Shaft portion-   151 Ball bearing-   161 Movable magnet-   161 c Magnetic pole switching portion-   200 Drive Unit-   210 Core body-   211 First core body-   212 Second core body-   220 Coil body-   221 First coil body-   222 Second coil body-   230 Bridging core-   240 Magnet position holding portion-   250 Fixing Plate-   300A, 300C, 300D Scanner system-   301, 411 Laser emitting unit-   302 Laser control unit-   304 Position control signal calculation unit-   410 Laser Unit-   412 Laser light receiving unit

The invention claimed is:
 1. A rotary reciprocating drive actuator comprising: a base portion; a movable magnet fixed to a shaft portion to which a movable object is connected; and a drive unit having a core body and a coil body for generating a magnetic flux in the core body when current is supplied, and driving the movable magnet in a rotary reciprocating manner by an electromagnetic interaction between the magnetic flux generated from the core body and the movable magnet, wherein the movable magnet is formed in a ring shape, and is configured by alternately magnetizing an even number of magnetic poles forming an S-pole and an N-pole at an outer periphery of the shaft portion; a number of magnetic poles of the core body and a number of magnetic poles of the movable magnet are equal to each other; an even number of magnetic poles of the core body is respectively arranged to face the movable magnet with an air gap therebetween on the outer peripheral side of the shaft portion; the drive unit is provided with a magnet position holding portion which is a magnetic material provided to face the movable magnet and magnetically attracts the movable magnet to a reference position; a pair of wall portions is erected on the base portion to rotatably support the shaft portion via a bearing, and the movable object is disposed between the pair of wall portions; and the drive unit is attached to one wall portion of the pair of wall portions, and an angle sensor portion for detecting the rotation angle of the shaft portion is attached to the other wall portion of the pair of wall portion; wherein the reference position at which the magnet position holding portion magnetically attracts the movable magnet is a rotational center position of the rotating reciprocation of the movable magnet.
 2. The rotary reciprocating drive actuator according to claim 1, wherein the angle sensor portion is attached to an outer surface side of the other wall portion.
 3. The rotary reciprocating drive actuator according to claim 1, wherein the movable magnet has an even number of magnetic poles magnetized at equal intervals at the outer periphery of the shaft portion.
 4. The rotary reciprocating drive actuator according to claim 1, wherein the magnet position holding portion is a magnet.
 5. The rotary reciprocating drive actuator according to claim 1, wherein the magnet position holding portion has convexly projected magnetic poles provided on the core body.
 6. The rotary reciprocating drive actuator according to claim 1, wherein the magnet position holding portion is disposed at a position between the even number of magnetic poles of the core body and at a position facing the movable magnet in the radial direction.
 7. The rotary reciprocating drive actuator according to claim 1, wherein the core body has an even number of core portions arranged at positions where the movable magnet is sandwiched, and the coil body is arranged so that a coil is wound around each of the core portions.
 8. The rotary reciprocating drive actuator according to claim 1, wherein the movable object is a mirror that reflects a scanning light.
 9. A scanner system comprising: the rotary reciprocating drive actuator according to claim 8; and a laser emitting unit or a laser emitting and receiving unit disposed in the base portion. 